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Biologia 63/6: 928—935, 2008 Section Botany DOI: 10.2478/s11756-008-0144-6

Use of desmids to assess the natural conservation value of a Hungarian oxbow (Malom-Tisza, NE-Hungary)* Enik˝ o Krasznai1 , Gizella Fehér2 , Gábor Borics3 , Gábor Várbíró3 , István Grigorszky4 & Béla Tóthmérész1 1

Debrecen University, Department of Ecology, Egyetem tér 1, H-4010 Debrecen, Hungary; e-mail: [email protected] Lower Danube Valley Directorate for Environment and Water, Széchenyi u 2/C, H-6500 Baja, Hungary 3 Environmental Protection, Nature Conservation and Water Authority, Trans-Tiszanian Region, Hatvan u. 16, H-4025 Debrecen, Hungary 4 Debrecen University, Department of Hydrobiology, Egyetem tér 1, H-4010 Debrecen, Hungary 2

Abstract: A method recently proposed by Coesel that uses the desmid flora to assess the conservation value of aquatic habitats was applied to an alkaline and hypertrophic oxbow of the Upper Tisza river (NE Hungary). According to the macrophyte community the oxbow contains two distinct habitats, both of which provide suitable conditions for the development of a rich desmid flora. High temporal and spatial differences in the algal flora were observed in periphyton and plankton samples taken in June and August 2004. The sample of Utricularia vulgaris periphyton collected in August was characterised by the most species-rich desmid flora. The conservation value of this sample was the maximum according to Coesel’s method. The latter also proved to be useful for the assessment of the conservation value of plankton net samples taken from among the macrophytes. The use of modified rarity value calculations as recently proposed by Fehér did not significantly affect the conservation value, but different enumeration methods to quantify the floristic diversity did result in different conservation values. We found that Coesel’s desmid based method is a useful tool for assessing the conservation value of the studied oxbow. Based our results the Coesel method’s applicability and usefulness depended on (i) the sampling location (open water or macrophytic region) samples were taken from open water or from macrophytic region; and (ii) species enumeration procedures (up to 400 specimens counted, or whole droplets counted). Key words: oxbow; Desmidiales; Coesel’s method; nature conservation value

Introduction Recently, the water quality assessments have been at the forefront of research (Rott et al. 2003; Gutowski et al. 2004; Padisák et al. 2006; Borics et al. 2007). During the last decades several methods were developed for the characterisation of the saprobic and trophic state of water bodies (J¨ arnefelt 1952; Teiling 1955; Heinonen 1980; Rosén 1981; H¨ornstr¨ om 1981; Tremel 1996; Lepist¨o 1999). Most of these studies were aimed at classifying the various standing and running water types on the basis of their pollution levels, and rank them on an absolute scale without consideration of their natural characteristics. As a consequence, the evaluation of naturally eutrophic water bodies is usually problematic. It is conceivable that by taking into account biological features like the diversity of the macrophyte flora, and that of the reptile, fish and bird fauna, a more accurate assessment of the biological and ecological value of several of these habitats is possible. Typical representatives of these water bodies are oxbows, alkaline

bog-lakes and marshlands which feature rich stands of macrophytes and benthic communities. For an evaluation of the quality of these habitats, a study of the benthic algae seems appropriate. For practical reasons, mostly diatom based metrics have been developed in recent years (Descy 1979; Watanabe et al. 1986; Schiefele & Schreiner 1991; Kelly et al. 1995; Lenoir & Coste 1996). Nevertheless non-diatom algae can also been used as indicators of biological integrity (Fjerdingstadt 1965; Palmer 1969; Hill et al. 2000; Blinn & Herbst 2003) although a number of problems have to be faced. Species identification in several groups of algae is difficult, and to decide what constitutes an individual (in the case of filamentous or colonial forms) can also be problematic. Desmids which are characteristic elements of epiphytic communities (John et al. 2002) can also be used in environmental assessments. Several species of this group are closely related to certain types of aquatic habitats, and may be used as indicators of changes of pH or nutrient supply (Coesel 1984; Borics et al. 1998;

* Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia.

c 2008 Institute of Botany, Slovak Academy of Sciences 

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929

Fig. 1. A. Map of Hungary. B. Map of the Tiszadob oxbow system: A – Darab-Tisza; B – Falu-Tisza; C – Malom-Tisza; D – Sz¨ ucs-Tisza; E – Fels˝ o-Darab-Tisza.

Fehér 2003). On the bases of occurrence, rarity and maturity of desmid species a method was developed by Coesel (2003) for assessing the nature conservation value (NCV) (Coesel 1998) of aquatic habitats. The Coesel method is presented for quantification of aquatic nature conservation value based on desmid assemblages present (Coesel 2001). Species richness (indicative of internal structural and functional differentiation of the ecosystem), the occurrence of rare taxa (often indicative of particular environmental conditions) and the presence of species indicative of ecosystem maturity are the parameters chosen to determine conservation value. For the sake of utility, schemes have been developed to transform the values scored for the various parameters to a simple scale ranging from 0 to 10, relative to regional and historical standards. During the first adaptation of this method for Hungary (Fehér 2007) the water qualities in the investigated lenitic waters were classified as oligotrophic to meso-eutrophic by trophic status based on desmid taxa. The goal of our study was to investigate the applicability of the method of Coesel (2003) to the Malom-Tisza oxbow (Hungary). The large numbers of the Hungarian natural standing waters belong to the “oxbow type” (Dévai et al. 1999; G˝ori et al. 2000). The macrophyte biodiversity indicates that the MalomTisza oxbow has a high natural value. In this study we tried to find answers to the following questions. (i) Are desmids important elements of the microflora of shallow, alkaline, hypertrophic oxbows? (ii) What kind of NCV values characterise the Malom-Tisza oxbow? (iii) Do the NCV values change during the course of the summer? (iv) Are there any differences in the NCV values between the different substrates? (v) Do the NCV values change after applying Fehér’s (2007) modified rarity values? (vi) What are the differences, if any, in the NCV values if different species enumeration methods are used? Material and methods The investigated oxbow lies in the middle of the Tisza valley (110 m a.s.l.) in the neighbourhood of the village of Tiszadob (Fig. 1A). The eleven kilometres long oxbow is divided into five sections (A, B, C, D and E; Fig. 1B) by dams. Three sections (B, C and D) can be found outside the embankments. The others (A and E) are on the floodplain. The largest section is the Malom-Tisza oxbow (C).

Table 1. Chemical parameters of the Malom-Tisza oxbow at sampling points 1, 5 and 7 (cf. Fig. 2). June 1

5

August 7

1

5

7

( ◦C)

Temperature 21.2 21.3 21.2 22.4 22.6 22.4 pH 7.93 7.51 8.56 7.61 7.33 7.39 Conductivity (µS cm−1 ) 283 289 287 299 297 295 Chlorophyll a (µg L−1 ) 10.7 2.2 2.3 5.5 5.3 7.6 −1 ) NH+ 0.2 0.17 0.18 0.17 0.24 0.23 4 (mg L −1 ) NO− 2 (mg L

−1 ) NO− 3 (mg L PO4-P (µg L−1 ) COD-Mn (mg L−1 )

0

0

0

0

0

0.01

1.9 40 10.6

2.1 30 9.3

2.1 40 9.8

2.5 60 8.9

2.4 70 8.6

2.4 60 10.7

Physical characteristics of the Malom-Tisza oxbow include: length 4.2 km, average width 80 m, surface area 46 hectares, average depth 3 m, maximum depth 12.5 m. Most of the oxbow is a typical pelagic ecosystem; at the eastern section of the oxbow a unique macrophyte association is present which covers almost the entire eastern lake-basin. This association (Calamagrosti-Salicetum cinereae Thelypteridosum palustris using Braun-Blanquet’s (1964) phytosociological terminology) is the result of the ageing process of water bodies and probably has always been a characteristic association of Hungary’s shallow lakes. For physico-chemical analyses (Table 1) water samples were taken from the immediate surface layer at sampling points 1, 5 and 7 and for phytoplankton investigations at points 1–7 of the oxbow (Fig. 2) on 24 June and 25 August 2004. Phytoplankton samples were obtained by filtering 10 L water through a plankton net (mesh size 20 µm). For the examination of the periphyton parts of macrophytes were collected. When different macrophyte species of smaller size (Spirodela, Lemna spp., Riccia sp.) occurred in a small area, so-called “mixed samples” were also taken, pressing the water from the macrophytes by hand and filtered it through the net (Fig. 2). The samples collected and their attributes are shown in Table 2. Samples were fixed with Lugol’s solution. The periphyton samples were shaken and allowed to settle in 100 mL cylinders. Two 20 µL droplets of the settled materials were investigated with LEICA DMRB microscope equipped with brightfield, phase-contrast and Nomarski interference contrast optics. Two different enumeration methods were used to estimate the species richness of the samples: (i) counting up to 400 specimens, (ii) counting the whole volume of droplets. We also calculated the difference in the number of species based on the two enumeration methods. For the

E. Krasznai et al.

930 Table 3. Number of observed taxa.

number of taxa June

Fig. 2. Sampling locations in the Malom-Tisza oxbow. 1 – boglake; 2 – north of bog-lake; 3 – margins of the Salici-Alnetum (floating islands); 4 – right side of the Salici-Alnetum (floating islands); 5 – pools in Salici-Alnetum (floating islands); 6 – lagzone; 7 – at the shore of Malom-Tisza.

Table 2. List of samples and their attributes. Sampling location designations 1–7 as in Fig. 2 Code

Type of the sample

UN 06 CP 06 PP 06 NM 06 SM 06 PB 06 NB 06 PL 06 SL 06 NL 06 ML 06 PS 06 NS 06 MS 06 UN 08 CP 08 NP 08 MP 08 VP 08 UP 08 HP 08 P1P 08 P2P 08 PR 08 SR 08 MR 08 PB 08 NB 08 PS 08 NS 08 MS 08

Utricularia periphyton Calliergonella periphyton plankton netplankton Salvinia periphyton plankton netplankton plankton Salvinia periphyton netplankton mixed periphyton plankton netplankton mixed periphyton Utricularia periphyton Calliergonella periphyton netplankton mixed periphyton Myriophyllum periphyton Utricularia periphyton Hydrocharis periphyton plankton plankton plankton Salvinia periphyton mixed periphyton plankton netplankton plankton netplankton mixed periphyton

Sampling location

Date

2 5 5 3 3 1 1 6 6 6 6 7 7 7 2 5 5 5 5 5 5 5 5 4 4 4 1 1 7 7 7

24.06.2004. 24.06.2004. 24.06.2004. 24.06.2004. 24.06.2004. 24.06.2004. 24.06.2004. 24.06.2004. 24.06.2004. 24.06.2004. 24.06.2004. 24.06.2004. 24.06.2004. 24.06.2004. 25.08.2004. 25.08.2004. 25.08.2004. 25.08.2004. 25.08.2004. 25.08.2004. 25.08.2004. 25.08.2004. 25.08.2004. 25.08.2004. 25.08.2004. 25.08.2004. 25.08.2004. 25.08.2004. 25.08.2004. 25.08.2004. 25.08.2004.

identification of the taxa we used Coesel (1982, 1983, 1985, 1991, 1994, 1996), and Růžička (1977, 1981). The conservation value of the oxbow was determined according to Coesel (2001) which was based on the desmid flora. Determination of the index requires the following data: number of desmids species observed (d, usually referred to as diversity), rarity (r) scores and maturity (m) scores of the desmid species. Rarity and maturity scores are based on expert judgement proposed by Coesel  (2001). Dependr, m, and d scores ing on the pH-type of the water the are transformed to the so-called M , R and D scores based on the suggection of Coesel (2001). The NCV is the sum of D (ranging from 1–3), R (ranging from 1–3) and M (ranging from 1–4); therefore the maximum of the D + R + M scores is 10. The idea of nature conservation value has to

CYANOBACTERIA HETEROKONTOPHYTA Chrysophyceae Bacillariophyceae Xanthophyceae CHLOROPHYTA Chlorococcales Desmidiales Volvocales Other Chlorophyta EUGLENOPHYTA DINOPHYTA CRYPTOPHYTA Total

August

Total

15

20

26

4 33

4 33 2

4 39 2

44 64 5 3 4 6 3 181

48 67 4 4 14 11 1 208

60 78 5 4 15 11 3 247

connect with the rarity, replacement of component of the given ecosystem and the regeneration of the biocoenosis after any disturbance. It is evidence the nature conservation value elaborated in the Netherlands, is need to evaluation in other countries. On basis of detailed investigation of SouthHungarian water bodies’ rarity values (r) of the desmid species have been modified by Fehér (2007). This study is the Coesel method very first evaluation for Hungary. Our database has also been evaluated by the modified Coesel’s method. The R-values were calculated in two different ways: as published originally by Coesel (2001) and follow the Fehér (2007) suggested modifications for indicator value based on Desmidiales taxa occurrences in Hungary, and with the modification according to Fehér (2007).

Results Floristic composition Altogether 247 taxa of algae were identified in 30 samples from the Malom-Tisza oxbow. The floristic compositions of the samples taken in June and August were slightly different (Table 3). The species number of Cyanobacteria, Euglenophyta and Dinophyta doubled in August. The species number of Euglenophyta (4) in June was very low. The microflora was dominated by Chlorophytes (147 taxa) and Bacillariophyceae (39). The number of desmids was surprisingly high: 78 (Table 4). Desmids that were present in at least 75% of the different habitats included Cosmarium phaseolus, C. subprotumidum var. pyramidale, Sphaerozosma vertebratum, Staurastrum furcatum, S. polymorphum, S. tetracerum and Xanthidium antilopaeum. Conservation value of the oxbow The differences in conservation values of the June and August samples were negligible (Figs 3, 4). The average conservation values (NCV) were 6.3 in June and 6.5 in August (based on the whole droplets method). NCV values ranged between 2 and 8 in June, and between 3 and 10 in August. The theoretical maximum of the NCV (10) was found in the periphyton sample of Utricularia vulgaris L., taken from the north of the bog-lake

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Fig. 3. NCV scores of the June samples (sample codes as in Table 2). (A) up to 400 specimens counted, (B) whole droplets counted. C – NCV calculated by Coesel’s method; F – NCV calculated by Fehér’s method.

(Fig. 2, map) in August. Differences of the NCV values between the samples are largely caused by the different R and M values, because D was almost constant (score 2) in every sample. Habitat/Sampling areas Due to the very low number of taxa observed, the NCV values of the open water proved to be very low too (NCV = 3). Higher values characterised the periphyton and the plankton net samples that were taken from small pools with a dense macrophyte vegetation. With respect to the number of observed species and the calcu-

lated NCV values, the periphyton sample of Utricularia vulgaris showed the highest scores (Fig. 4B). Different sample enumeration methods The two different sample enumeration methods (counting up to 400 specimens and analysis of the whole volume of the droplets) resulted in slight differences in the conservation values (Fig. 4). Approximately half of the samples showed an increase of one point. Nevertheless in the case of the Utricularia vulgaris sample in August, due to the more detailed microscopic analysis, a more substantial increase by 2 points was observed.

E. Krasznai et al.

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Table 4. Desmidiales flora of the oxbow. * rare taxa in Hungary (Fehér 2007). Sampling location designations 1–7 as in Fig. 2. Sampling locations Taxon 1 *Actinotaenium turgidum (Bréb.) Teil. Closterium aciculare T. West Closterium acutum Bréb. Closterium acutum var variabile (Lemmerm.) Willi Krieg. Closterium dianae Ehrenb. Closterium ehrenbergii Menegh. ex Rafls Closterium incurvum Bréb. Closterium moniliferum (Bory) Ehrenb. ex Rafls Closterium sp. 1 Closterium sp. 2 Closterium venus K¨ utz. ex Ralfs Cosmarium botrytis Menegh. et Ralfs *Cosmarium connatum Bréb. Cosmarium contractum Kirchn. Cosmarium contractum Kirchn. var. contractum Cosmarium contractum Kirchn. var. ellipsoideum (Elfv.) W. et G.S. West Cosmarium contractum Kirchn. var. retusum (W. et G.S. West) Krieg. et Gerl. Cosmarium contractum Kirchn. var rotundatum Borge Cosmarium crenulatum Ralfs ex Ralfs. Cosmarium depressum (N¨ ageli) P. Lundell *Cosmarium fastidiosum W. et G. S. West cf. Cosmarium formosulum Hoff Cosmarium granatum Bréb. ex Ralfs Cosmarium humile (F. Gay) Nordst. Cosmarium margaritiferum (Turpin) Menegh. ex Ralfs Cosmarium moniliforme (Turpin) ex Ralfs *Cosmarium notatum (Gr¨ onbl.) Coes. Cosmarium phaseolus Bréb. ex Ralfs Cosmarium portianum W. Archer *Cosmarium pseudoretusum Ducell v. inaequalipellicum (W. et G. S. West) Krieg. et Gerl. *Cosmarium pseudoretusum Ducell. var pseudoretusum Krieger et Gerloff Cosmarium punctulatum Bréb. cf. Cosmarium pygmaeum W. Archer cf. *Cosmarium pyramidatum Bréb. cf. Cosmarium regnellii Wille Cosmarium regnellii Wille var. minimum B. Eichler et Gutw. Cosmarium regnellii Wille var. regnellii *Cosmarium regnesi Reinsch var. montanum Schmidle Cosmarium reniforme (Ralfs) W. Archer Cosmarium subprotumidum Nordst. var pyramidale Coes. Cosmarium subprotumidum Nordst. var subprotumidum West et West Cosmarium subtumidum Nordst. Cosmarium subundulatum Wille *Cosmarium tetraophthalmum Bréb. Cosmarium turpinii Bréb. Desmidium aptogonum Bréb. Desmidium swartzii C. Agardh Euastrum denticulatum (Kirchn.) F. Gay *Euastrum germanicum (Schmidle) Willi Krieg. Heimansia pusilla (Hilse) Coes. Micrasterias crux-melitensis (Ehrenb.) Hassal Pleurotaenium trabecula var. trabecula (Ehrenb.) N¨ ageli *Sphaerozosma laeve (Nordst) Thom. *Sphaerozosma vertebratum (Bréb.) Ralfs Spondylosium planum (Wolle) W. et G. S. West Staurastrum anatinum Cooke et Wills *Staurastrum bieneanum Rabenh. *Staurastrum boreale W. et G. S. West *Staurastrum boreale W. et G. S. West var. quadriradiatum Kors. *Staurastrum furcatum (Ehrenb.) Bréb. Staurastrum furcatum (Ehrenb.). Bréb. (4 arms) Staurastrum gladiosum W. B. Turner Staurastrum hystrix Ralfs Staurastrum lunatum Ralfs Staurastrum manfedtii Delponte Staurastrum orbiculare (Ehrenb.) Ralfs Staurastrum polymorphum Bréb. *Staurastrum quadrangulare Ehrenb. ex Ralfs

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Table 4. (continued). Sampling locations Taxon

*Staurastrum smithii G. M. Smith *Staurastrum subavicula (W. West) W. et G. S. West Staurastrum teliferum Ralfs Staurastrum tetracerum Ralfs Staurodesmus cuspidatus (Bréb. ex Ralfs) Teil. Staurodesmus dejectus (Bréb. ex Ralfs) Staurodesmus dejectus (Bréb. ex Ralfs) v. apiculatus (Bréb.) Teil. *Staurodesmus glaber (Ehrenb. ex Ralfs) Teil. Xanthidium antilopaeum (Bréb.) K¨ utz. *Xanthidium variabile (Nordst.) W. et G. S. West

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E. Krasznai et al.

934 Calculation of the rarity values Use of modified rarity values (Fehér 2007) did not significantly affect the value of the NCV-index (max. difference was ±1). Modification resulted in an increase of the NCV index by one point for those samples that originally had NCV values of 3 and 6. Samples that had very low and very high values were unaffected. A decrease of the NCV index was only found in sample SL06F, a periphyton sample from Salvinia natans (L.) All. taken in the lag-zone. Discussion The observed 247 algal taxa are indicative of a speciesrich microflora in the Malom-Tisza oxbow. The relative share of the desmids was high (78 taxa). Only two Hungarian floristic accounts are available in which a larger number of species were reported, namely from a rice field (Kol 1954) and from Baláta, the largest Hungarian bog-lake (Borics 2001), respectively. Several species that are considered to be acidophilic (e.g. Cosmarium margaritiferum, Staurastrum furcatum), acido-neutrophilic (e.g. Cosmarium contractum, Xanthidium antilopaeum), and prefer oligotrophic (e.g. Cosmarium pyramidatum, Teilingia excavata) or oligomesotrofic environments (e.g. Cosmarium pseudoretusum, Staurodesmus dejectus) were observed. It is not clear whether these unexpected findings are due to the limited knowledge about the tolerance of these species, or to the existence of ecotypes. Contrary to expectations, the NCV values of the late summer samples compared to those taken in June were not significantly higher. Species that are characteristic for mature periphyton assemblages (Coesel 1998) (e.g. Sphaerozosma vertebratum, Micrasterias crux-melitensis, Cosmarium regnessi, Desmidium swartzii) were already present in June; thus, the maturity and rarity values were almost identical. Nevertheless it is worth mentioning that a possibly higher score of the NCV (10) was observed only in August. Considerable differences in the NCV values of the microhabitats sampled were observed. The microhabitat of Utricularia vulgaris was characterised by the highest diversity and maturity values. Compared to other macrophytes like Myriophyllum verticillatum, Ceratophyllum demersum and C. submersum, the leave structure of Utricularia vulgaris is more delicate and provides an ideal habitat for periphytic assemblages. The plankton of pools with a rich vegetation are also characterised by high NCV values. Due to mechanical disturbances caused by the sampling procedure, a large number of desmids end up in the tychoplankton. We observed considerable differences between the two species enumeration methods. Analysis of the total volume of the droplets resulted in an approximately 20% increase in the species number. Nevertheless this increase did not result in a change of the D value (Figs 3, 4). We calculated the NCV values also with the modified “r” values as suggested by Fehér (2007), but this

resulted only in slight changes in the NCV values. The Malom-Tisza oxbow had a high NCV value which demonstrates that naturally hypertrophic systems can be valuable habitats. Our results demonstrate that different sampling strategies and enumeration methods only result in small differences in the natural values (NCV scores). Coesel (2001) has suggested that the method should be based on species and that the use of lower taxa should be avoided, but there are cases where lower taxa (forms, varieties) have different ecological requirements or behaviour. Our opinion based on the field experience of this study is that forms or varieties, provided they can be identified reliably, may be considered in NCV assessment studies. In conclusion, our results suggested that Coesel’s (2001) method was a useful tool for evaluating the NCV values of the Hungarian oxbow, but for wider acceptance of the method standardisation of the sampling and species enumeration procedures was needed. Acknowledgements Thanks are due to the Environmental Protection, Nature Conservation and Water Authority, Trans-Tiszanian Region, for their help with sampling and data analysis. This study was supported by the Hungarian National Science Foundation (OTKA No. K60452) and by a Bolyai János Research Fellowship of the Hungarian Academy of Sciences. References Blinn D.W. & Herbst D.B. 2003. Use of diatoms and soft algae as indicators of environmental determinants in the Lahontan Basin, USA. Annual Report to the California State Water Resources Board. 25 pp + appendices. Borics G., Padisák J., Grigorszky I., Oldal I., Péterfi L.I. & Momeu L. 1998. Green algal flora of the acidic bog-lake, Balátató SW Hungary. Biologia 53: 457–465. Borics G. 2001. A Baláta-tó és néhány hazai lápvíz algaflórájának f˝ obb jellemvonásai. PhD értekezés. Debreceni Egyetem. [Algological characteristics of the bog lake Baláta-tó, and other smaller Hungarian bog systems. In Hungarian with English summary] Borics G., Várbíró G., Kiss K.T., Grigorszky I., Krasznai E. & Szabó S. 2007 Possible evaluation of rheo-plankton for assessing the ecological status os rivers. Arch. Hydrobiol. Suppl. 161 Large Rivers 17: 465–486. Braun-Blanquet J. 1964. Pflanzensociologie, Springer, Wien. 865 pp. Coesel P.F.M. 1982. De Desmidiaceeén van Nederland. I. Fam. Mesotaeniaceae, Gonatozygaceae, Peniaceae. Wetensch. Meded. KNNV 153, Hoogwoud, 32 pp. Coesel P.F.M. 1983. De Desmidiaceeén van Nederland. II. Fam. Closteriaceae. Wetensch. Meded. KNNV 157, Hoogwoud, 49 pp. Coesel P.F.M. 1984. The significance of desmids as indicators of the trophic status of freshwaters. Schweiz. Z. Hydrol. 45: 388–393. Coesel P.F.M. 1985. De Desmidiaceeén van Nederland. III. Fam. Desmidiaceae. Wetensch. Meded. KNNV 170, Hoogwoud, 70 pp. Coesel P.F.M. 1991. De Desmidiaceeén van Nederland. IV. Fam. Desmidiaceae (2). Wetensch. Meded. KNNV. 202, Hoogwoud, 89 pp. Coesel P.F.M. 1994. De Desmidiaceeén van Nederland. V. Fam. Desmidiaceae (3). Wetensch. Meded. KNNV. 210, Hoogwoud, 55 pp.

Desmids to asses natural value Coesel P.F.M. 1996. De Desmidiaceeén van Nederland. VI. Fam. Desmidiaceae (4). Wetensch. Meded. KNNV. 215, Hoogwoud, 92 pp. Coesel P.F.M. 1998. Sieralgen en natuurwaarden. Wetenschappelijke Mededeling KNNV nr. 224. Uitgeverij Koninklijke Nederlandse Natuurhistorische Vereniging, Utrecht, 56 pp. Coesel P.F.M. 2001. A method for quantifying conservation value in lentic freshwater habitats using desmids as indicator organisms. Biodiversity & Conservation 10: 177–187. Descy J.P. 1979. A new approach to water quality estimation using. diatoms. Nova Hedwigia Beih. 64: 305–323. Dévai Gy., Végvári P., Nagy S. & Bancsi I. 1999. Az ¨ okológiai vízmin˝ osítés elmélete és gyakorlata. 1. rész (Ecological water quality assessment, theory and practice, 1. part). Acta Biol. Debrecina, Suppl. Oecol. Hung. 10/1, 216 pp. Fehér G. 2003. The desmid flora of some alkaline lakes and wetlands in Southern Hungary. Biologia 58(4): 671–683. Fehér G. 2007. Use of Desmidiales flora for monitoring rivers: a case of South-Hungarian waters. Arch. Hydrobiol. Suppl. Large Rivers 17/3–4, 161/3–4: 417–433. Fjerdingstadt E. 1965. Some remarks on a new saprobic system, in:Biological Problems in Water Pollution, 3 rd Seminar, USPHS. Publication 999-WP-25, pp. 232–235. G˝ ori Sz., Aradi Cs., Dévai Gy. & Nagy S. 2000. 2.1. Principles and methodology of integrated categorisation of water bodies and wetlands demonstrated on backwaters, pp. 91–97. In: Gallé. L. & K¨ orm¨ oczi L. (eds), Ecology of river valleys. Tiscia, Szeged. Gutowski A., Foerster J. & Schaumburg, J. 2004. On the use of benthic algae, excluding Diatoms and Charales, for the assessment of the ecological status of running fresh waters. A case history from Germany. Oceanol. Hydrobiol. Stud., Gdansk, 33/2: 3–15. Heinonen P. 1980. Quantity and composition of phytoplankton in Finish inland waters. Publ. Water Res. Inst. 86/1–2: 29–31. Hill B.H., Herlihy A.T., Kaufmann P.R., Stevenson R.J., McCormick F.H. & Johnson C.B. 2000. Use of periphyton assemblage data as an index of biotic integrity. J. North Amer. Benthol. Soc. 19: 50–67. H¨ ornstr¨ om E. 1981. Trophic characterisation of lakes by means of quantitative phytoplankton analysis. Limnologica 13: 249– 361. J¨ arnefelt H. 1952. Plankton als Indikator der Trophiegruppen der Seen. Ann. Acad. Sci. Fenn. A IV, Biol. 18: 1–29. John D.M., Whitton B.A. & Brook A.J. 2002. The freshwater algal flora of the British Isles: An identification guide to freshwater and terrestrial algae. Cambridge University Press and The Natural History Museum, Cambridge, 702 pp.

935 Kelly M.G., Penny C.J. & Whitton B.A. 1995. Comparative performance of benthic diatom indices used to assess river water quality. Hydrobiologia 302: 179–188. Kol E. 1954. Algológiai és hidrobiológiai vizsgálatok a Szarvas k¨ ornyéki rizstelepeken (Algological characteristics of rice fields. In Hungarian). Ann. Hist.-Nat. Mus. Nat. Hung.N.S. 5: 49–104. Lenoir A. & Coste M. 1996. Development of practical diatomic index of overall water quality applicable to the French National Water Board Network, pp. 29–43. In : Whitton B.A. & Rott E. (eds), Use of Algae for monitoring Rivers II, Institut f¨ ur Botanik, Universit¨ at Innsbruck. Lepist¨ o L. 1999. Phytoplankton assemblages reflecting the ecological status of lakes in Finland. Monographs of the Boreal Environment Research 16, Tampere. Padisák J., Grigorszky I., Borics G. & Soróczki-Pintér É. 2006. Use of phytoplankton assemblages for monitoring ecological status of lakes within the Water Framework Directive: the assemblage index. Hydrobiologia 553: 1–14. Palmer C.M. 1969. A composite rating of algae tolerating organic pollution. J. Phycol. 5: 78–82. Rosén G. 1981. Phytoplankton indicators and their relation to certain chemical and physical factors. Limnologica 13: 263– 290. Rott E., Pipp E. & Pfister P 2003. Diatom methods developed fort he river quality assessment in Austria and a cross-check against numerical trophic indication methods used in Europe. Algol. Stud. 110: 91–115. Růžička J. 1977. Die Desmidiaceen Mitteleuropas. Band 1. Lief. 1. E. Scweizerbart’sche Verlagsbuchhandlung, Stuttgart. Růžička J. 1981. Die Desmidiaceen Mitteleuropas. Band 1. Lief. 2. E. Scweizerbart’sche Verlagsbuchhandlung, Stuttgart. Schiefele S. & Schreiner C. 1991. Use of diatoms for monitoring nutrient enrichment, acidification and impact of salt in rivers in Germany and Austria, pp. 103–110. In: Whitton B.A., Rott E. & Friedrich G. (eds) Use of algae for monitoring rivers, Institut f¨ ur Botanik, Univ. Innsbruck. Teiling E. 1955. Some mesotrophic phytoplankton indicators. Int. Vereinigung Theor. Limnol. Verh. 12: 212–215. Tremel B. 1996. Determination of the trophic state by qualitative and quanttitative phytoplankton analysis in two gravel pit lakes. Hydrobiologia 323: 1–38. Watanabe T., Asai K. & Houki A. 1986. Numerical estimation to organic pollution of flowing water by using the epilithic diatom assemblage. Diatom Assemblage Index (DAIpo). Sci. Total Environm. 55: 209–218. Received September 1, 2007 Accepted March 17, 2008